Conventionally, for a rotor of an induction motor, there have been proposed many shapes such as shapes of slots and shapes for reducing a power factor, a stray load loss, noise, and the like by providing slits on an outer circumference.
For example, a shape of a rotor is proposed as follows for a high-performance induction motor including a rotor iron core having a plurality of slots and a secondary conductor contained in these slots of the rotor iron core and formed by aluminum die casting. In this induction motor, slits that are not coupled to these slots are provided on a rotor surface side of enclosed slots of the rotor iron core, respectively, and each of these slits is set to have a circumferential dimension in a range from 1.0 millimeter to 3.5 millimeters and a radial dimension in a range from 1.0 millimeter to 2.5 millimeters so as to be able to always reduce its power factor, stray load loss, noise, and the like (see, for example, Patent Literature 1).